The present invention relates to a magnetic roller conveyor for transporting magnetically conductive objects. More particularly, it relates to such magnetic roller conveyor which comprises at least two magnetically conductive rollers, and a magnetic system including permanent magnets located adjacent both axial end portions of the rollers.
Magnetic roller conveyors have been proposed which comprise iron base plates and a plurality of permanent magnets each located at a distance from the respective roller. A free pole of each of the magnets outwardly surrounds the outer circumferential surface of the respective roller so that an air gap is formed between the former and the latter, and therefore no direct magnetic connection is provided between the above members. Such known construction possesses the following disadvantages. In this case magnetic lines of force must pass through the gap formed between the magnets and the respective rollers, and particularly through two gaps for each roller since each roller is provided with two magnets located adjacent the spaced axial ends thereof. This is aggravated by existence of a working air gap formed between the adjacent roller which working gap is more or less overlapped by the transported objects positioned on the roller conveyor. The working air gap and the air gap formed between the magnets and the rollers results in a great magnetic dissipation which weakens the magnetic field of the system and, therefore, reduces the magnetic force of attraction of the roller conveyor.
Another disadvantage of the known construction is that the air gap between the rollers and the magnets becomes clogged by readily magnetizable particles which are contained in ambient dust or are drawn along by the conveyor during the operation of the same. The above clogging of the air gap between the rollers and the magnets hinders and even blocks rotation of the rollers. Finally, such air gap interrupts the magnetic path whereby the magnetic system is permanently demagnetized which results in weakening of the magnetic efficiency of the magnetic roller conveyor.